Chemical Coordination in plants Flashcards
What is tropism?
The growth response of a plant to a directional stimuli
What are examples of directional stimuli?
Light and gravity as they act in a particular direction
What is growth towards stimulus?
Positive tropism
What is growth away from stimulus?
Negative tropism
What is light in one direction called?
Uni-directional
What is light that shines on the plant evenly from every direction called?
Uniform light
What is the result of phototropism? (light)
- Shoots: positive as the shoots grow towards the light source
- Roots: negative, most roots don’t respond but if they do they grow away from the light source
What is the result of geotropism (gravity)
- Shoots: negative as the shoots grow away from the direction of gravity
- Roots: positive as the roots grow towards the direction of gravity
What is the result of hydrotropism (water)
- Shoots: none
- Roots: positive, some species may grow towards water however only a few
What are auxins?
Plant growth hormones
Describe the response to light
- Auxins are released from the tip of the plant
- They travel along the part of the plant which is NOT exposed to the sun/light
- They initiate growth on that side causing the plant to bend towards the light
Describe what happens with the auxins in geotropism?
- Auxins accumulate on the lower side of the shoot and STIMULATE growth, causing the shoot to bend upwards
- Auxins accumulate on the lower side of the root INHIBITING growth and causing the root to bend downwards
- The receptors in the root and shoots interpret the auxins differently which causes them to grow in different directions
Do plants respond to stimuli?
Yes
